As an injection mold having improved cavity surface transfer properties, an injection mold having a heat insulating structure (Japanese Patent Laid-Open No. 53-86754) is conventionally known. The surface transfer properties of this injection mold are improved by interposing a heat insulating material layer between a thin metal layer forming the cavity surface and a backing material, thereby decreasing the cooling rate of an injection-molded product during injection molding.
Unfortunately, the above prior art has the following unsolved problem.
An injection mold uses sliding members, such as an ejector pin, slide core, and inclined core, having partial cavity surfaces which form portions of the cavity surface. Each of these sliding members is slidably guided by the sliding surface of an adjacent member which is adjacent to this sliding member, and protruded into the cavity or retracted into the adjacent member, i.e., linearly moved. This linear motion is repeated for each molding cycle. Consequently, a load such as the frictional force is repetitively exerted on the edge of a heat insulating coat with which the sliding member or adjacent member is coated. This causes easy peeling of the heat insulating coat.
The edge of the heat insulating coat with which the sliding member or adjacent member is coated is formed by masking or machining. Therefore, the adhesion of the edge is lowered by a load generated when the masking material is peeled or when machining is performed. This presumably further promotes .peeling.